removing conrod and piston - 200tdi

IrieLandy · Dec 6, 2009

Silly question for the day....

i'm trying to get my pistons out . the haynes says once the bottom half of the bigend has been removed and the top half lifted off the crankpin, you can push the conrod and piston up and out through the bore - well i know this may sound stupid but the big end doesnt fit through the bore!

am i missing something here?!

pos · Dec 6, 2009

Hello,

If I understand correctly, what you're saying is that you've removed the big end cap (that secures the con rod and bearing half to the crank shaft with two nuts), and you've also removed the head from the engine. Then, as you try to knock the piston up and out (if the engine is still in the vehicle) or down and out through the bore (if you have the engine removed from the vehicle), the big end of the con rod is too wide to fit through the cylinder?

That would immediately suggest to me that you've left the ladder frame in place (if your engine has one), or the engine has seen some major rebuild work in the past. If you look at the bottom of the engine and you observe the bores, can you see the entire core cylinder, or is there somthign obstructing the bore slightly as if to give the cylinder a straight edge, such as a support or a re-enforcement ladder for example? I'm not too sure whether the 200TDi has a ladder to remove.

If the bores look clear with no obstruction and you're certain that the big ends will not fit down the bore, I'd suggest that someone has had the pistons out before, and re-fitted non-standard con rods. If this is the case, you're looking at having to remove the crank shaft and then knocking the pistons out from the top of the engine. If you decide to take this option, make sure that you put a towel or two into the bores on top of the piston crown, so that when you whack it down and out of the bottom of the block, you don't damage the piston crown. It's a bit of a bugger of a way of removing a piston mind because it's not just as simple as dropping the crank shaft out. Your fly wheel is bolted directly too it which would mean taking the bell housing off - a total engine out job. Obviously, you'd then have to fit new crank shaft bearings and crank oil seals before re-fitting the crank shaft.

Pictures would be a great great help so that we can assess how to help you.

-Pos

CharlesY · Dec 6, 2009

NO NO NO!!!!

Do NOT try to knock pistons DOWN, because I believe some of them WILL NOT come out downwards, but by the time you discover that some of the rings will have cleared the bottoms of the bores. Piston STUCK!

You must be able to fit and remove pistons and rods FROM THE TOP! .
The big-end cap should NOT be on the rod when you do this.
The crank-pins of the cylinders must be UP as far as they can go (top dead centre) so the rod can align vertically in the bore - and it will be a very neat fit! The rod and piston will NOT come up and out unless you do this. Use a wooden dowel and a modest hammer to tap the rod up and out.

They will come out upwards if you do it this way. I betcha!

CharlesY

Draglink · Dec 6, 2009

CharlesY's right.

Also think of the wear caused by piston rings on cylinder wall. Obvious really.

IrieLandy · Dec 7, 2009

The engine is out of the vehicle (well actually hanging above it on a hoist) and the ladder frame has been removed - dont i wish i had a 300tdi?!

i will try moving the crankpin to TDC - maybe the conrod didnt fit through because it was at the wrong angle. have already had the piston sticking up above the top of the cylinder block to the point that the rings came out above and then found it stuck... prised the rings out and then pushed it back down - was planning on fitting new rings anyway!

i seriously hope i dont have to remove the crankshaft! was hoping not to have had to take the engine out at all since i recently put a new clutch in but the feckin ladder frame doesnt come off unless you can get to the 4 bolts under the flywheel housing - as far as i know mine's a 200tdi from a disco so dont know if its a thing particular to disco's, since the haynes manual says you CAN take the pistons out without removing the engine, when it mentions the ladder frame it says "undo the ten bolts securing the ladder frame" when in fact there are nine bolts that are accessible from underneath and then as i said 4 bolts securing it horizontally through the flywheel housing. so its either a mistake on the part of haynes or my engine's different to a standard defender 200tdi?!

will post some pics later on

CharlesY · Dec 7, 2009

IrieLandy said:
The engine is out of the vehicle (well actually hanging above it on a hoist) and the ladder frame has been removed - dont i wish i had a 300tdi?!

i will try moving the crankpin to TDC - maybe the conrod didnt fit through because it was at the wrong angle. have already had the piston sticking up above the top of the cylinder block to the point that the rings came out above and then found it stuck... prised the rings out and then pushed it back down - was planning on fitting new rings anyway!

i seriously hope i dont have to remove the crankshaft!

Hi,

I think you are on the right trail now.
You should NOT need to take the crankshaft out just to take out pistons and rods, and even if you did, the pistons will almost certainly NOT come out downwards anyway.
I think you will be surprised how neat a fit the big end of the con-rod is in the cylinder bore. Be aware that many conrods are NOT SYMMETRIC, and in such cases it is ABSOLUTELY VITAL they are fitted the right way, front to front. The rebuilt engine will be seized on assembly and if it is forced to start up (towing is the usual way) it will destroy the bores, pistons, conrods, big-end bearings and probably the crankshaft.

One of the main reasons for making engines with shorter strokes and therefore larger bores is to enable bigger big-ends to be used (fitted through the cylinders), thus allowing larger diameter crankpins on the crankshaft, and so a stronger crankshaft. Remember, the whole power of all the cylinders is taken by the last crankpin on the crankshaft, so it needs to be strong enough to take the whole power output, not just the power of its own cylinder above it.

CharlesY

jamescronin · Dec 8, 2009

The big end will be quite a tight fit through the bore. Oversized con rods will be. Pain to fit in the first place as reinserting them from the bottom with new rings would be a bug*er and a half, so I suspect this is not the case, and like previously stated I bet it's the angle your trying to get them through at. Have a play but don't force them

CharlesY · Dec 8, 2009

jamescronin said:
The big end will be quite a tight fit through the bore.

CORRECT!

Oversized con rods will be.
HUH? What's an over-size conrod?

Pain to fit in the first place as reinserting them from the bottom with new rings would be a bug*er and a half,

Believe it! It is IMPOSSIBLE!!! There isn't space to get a piston up to the bottoms of the bores.

so I suspect this is not the case, and like previously stated I bet it's the angle your trying to get them through at. Have a play but don't force them

Pistons and rods are fitted from the top, DOWNWARDS, and removed upwards. You will see why when you get one out. Offer the piston to the bore from below and tell us what chance there is of fitting them from there.
For a start, how would you compress the rings?
You do have a ring compressor, right?

CharlesY

jamescronin · Dec 8, 2009

What i ment by over-sized and i stand corrected on the terminology was 'extra strenght' i.e. fatter ones, which i have seen advertised, but I guess are not avalible - what I was trying to say - which you seem to have put much more eliquantly was that they must have gone in from the top, so should come out from the top.......................

As for ring compressor - i have one , not sure about IrieLandy - they only cost around £7-8 quid from the car accessory shop, but i would get a decent one - not any of this cheep **** as last time i used one of those i spent a good 3 hours just trying to get the bladdy thing to compress the first one - gave up and got a better one - and that was one a 1.25L petrol engine

removing conrod and piston - 200tdi

IrieLandy

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Draglink

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